U.S. patent application number 12/880017 was filed with the patent office on 2011-06-16 for catadioptric system, aberration measuring apparatus, method of adjusting optical system, exposure apparatus, and device manufacturing method.
This patent application is currently assigned to Nikon Corporation. Invention is credited to Yasuhiro Ohmura.
Application Number | 20110143287 12/880017 |
Document ID | / |
Family ID | 43332854 |
Filed Date | 2011-06-16 |
United States Patent
Application |
20110143287 |
Kind Code |
A1 |
Ohmura; Yasuhiro |
June 16, 2011 |
CATADIOPTRIC SYSTEM, ABERRATION MEASURING APPARATUS, METHOD OF
ADJUSTING OPTICAL SYSTEM, EXPOSURE APPARATUS, AND DEVICE
MANUFACTURING METHOD
Abstract
According to one embodiment relates to an optical system
radially downsized and corrected well for aberration and is
applicable, for example, to an aberration measuring apparatus for
measuring wavefront aberration of a liquid immersion projection
optical system. A catadioptric system of a coaxial type is provided
with a first optical system which forms a point optically conjugate
with an intersecting point with the optical axis on a first plane
intersecting with the optical axis, on a second plane, and a second
optical system which guides light from the first optical system to
a third plane. The first optical system has a first reflecting
surface arranged at or near the first plane, a second reflecting
surface having a form of an ellipsoid of revolution the two focuses
of which are aligned along the optical axis in a state in which one
focus is located at or near a first light transmissive portion, and
a medium filling an optical path between the first reflecting
surface and the second reflecting surface. The first light
transmissive portion is formed in a central region of the first
reflecting surface including the optical axis and a second light
transmissive portion is formed in a central region of the second
reflecting surface including the optical axis. The medium has the
refractive index of not less than 1.3. The second optical system
has a plurality of lenses.
Inventors: |
Ohmura; Yasuhiro; (Saitama,
JP) |
Assignee: |
Nikon Corporation
|
Family ID: |
43332854 |
Appl. No.: |
12/880017 |
Filed: |
September 10, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61272335 |
Sep 14, 2009 |
|
|
|
Current U.S.
Class: |
430/325 ; 355/67;
356/124; 359/728 |
Current CPC
Class: |
G03F 7/70341 20130101;
G02B 17/0856 20130101; G02B 17/0808 20130101; G03F 7/70225
20130101; G03F 7/706 20130101; G02B 17/0892 20130101 |
Class at
Publication: |
430/325 ;
359/728; 355/67; 356/124 |
International
Class: |
G03F 7/20 20060101
G03F007/20; G02B 17/08 20060101 G02B017/08; G03B 27/54 20060101
G03B027/54; G01B 9/00 20060101 G01B009/00 |
Claims
1. A catadioptric system of a coaxial type, comprising: a first
optical system which forms a point optically conjugate with an
intersecting point with the optical axis on a first plane
intersecting with the optical axis, on a second plane; and a second
optical system which guides light from the first optical system to
a third plane, wherein the first optical system has: a first
reflecting surface arranged at or near a position of the first
plane, the first reflecting surface having a first light
transmissive portion formed in a central region including the
optical axis; a second reflecting surface having a form of an
ellipsoid of revolution the two focuses of which are aligned along
the optical axis in a state in which one focus is located at or
near the first light transmissive portion, the second reflecting
surface having a second light transmissive portion formed in a
central region including the optical axis; and a medium filling an
optical path between the first reflecting surface and the second
reflecting surface, the medium having a refractive index of not
less than 1.3, wherein the second optical system has a plurality of
lenses, wherein light from the intersecting point between the first
plane and the optical axis travels through the first light
transmissive portion, is successively reflected by the second
reflecting surface and the first reflecting surface, and then
travels through the second light transmissive portion to enter the
second optical system, and wherein all reflecting surfaces and all
refracting surfaces of the catadioptric system are arranged on an
optical axis extending linearly.
2. The catadioptric system according to claim 1, wherein the second
optical system has a first lens disposed nearest to the first
optical system, with a convex surface on the third plane side.
3. The catadioptric system according to claim 2, wherein the first
lens has a positive refractive power.
4. The catadioptric system according to claim 1, wherein the first
optical system has an enlargement magnification ratio from the
first plane toward the second plane.
5. The catadioptric system according to claim 1, wherein the first
reflecting surface is formed in a planar shape and the second
reflecting surface is formed in a prolate spheroid shape.
6. The catadioptric system according to claim 5, wherein an axis of
revolution of the prolate spheroid agrees with the optical
axis.
7. The catadioptric system according to claim 1, wherein the second
light transmissive portion is arranged at or near a position of the
second plane.
8. The catadioptric system according to claim 1, comprising: a
single optical member a shape of which is defined by a plurality of
faces, wherein the first reflecting surface is formed on one face
of the single optical member and wherein the second reflecting
surface is formed on another face of the single optical member.
9. The catadioptric system according to claim 1, comprising: an
optical structure comprised of a first member and a second member a
shape of each of which is defined by a plurality of faces and which
are cemented to each other, wherein the first reflecting surface is
formed on a face different from a face cemented to the second
member out of the plurality of faces of the first member and
wherein the second reflecting surface is formed on a face different
from a face cemented to the first member out of the plurality of
faces of the second member.
10. The catadioptric system according to claim 1, wherein the conic
coefficient .kappa. defining the ellipsoid of revolution of the
second reflecting surface satisfies the following condition:
-0.20<.kappa.<-0.08.
11. The catadioptric system according to claim 1, wherein the
second optical system includes a refracting optical system.
12. The catadioptric system according to claim 1, wherein the
second optical system includes an imaging optical system which
forms a point optically conjugate with an intersecting point
between the second plane and the optical axis, on the third
plane.
13. The catadioptric system according to claim 1, further
comprising: a shield member for preventing the light from the
intersecting point between the first plane and the optical axis
from reaching the third plane through the second light transmissive
portion without being reflected by the second reflecting
surface.
14. The catadioptric system according to claim 13, wherein the
shield member is arranged in an optical path between the first
optical system and the third plane.
15. The catadioptric system according to claim 13, wherein the
second optical system includes an imaging optical system which
forms a point optically conjugate with an intersecting point
between the second plane and the optical axis, on the third plane,
and wherein the shield member is arranged at or near a position of
a pupil of the second optical system.
16. The catadioptric system according to claim 1, wherein the
second plane is located in a gas optical path between the first
optical system and the second optical system.
17. The catadioptric system according to claim 1, wherein an
optical member forming at least a part of the first optical system
and an optical member forming at least a part of the second optical
system are cemented to each other, and wherein the second plane is
located in one optical member out of the pair of optical members
cemented to each other.
18. The catadioptric system according to claim 1, wherein the
catadioptric system satisfies the following condition:
0.95<L/D<1.05, where D is a distance along the optical axis
between an extension of the first reflecting surface and an
extension of the second reflecting surface and L a distance along
the optical axis between the extension of the first reflecting
surface and the second plane.
19. An aberration measuring apparatus configured to measure
aberration of an optical system to be examined, comprising: the
catadioptric system according to claim 1.
20. The aberration measuring apparatus according to claim 19,
wherein the catadioptric system is arranged so that the first plane
coincides with an image plane of the optical system to be
examined.
21. A method of adjusting an optical system, comprising: using
aberration information obtained by the aberration measuring
apparatus according to claim 19, to adjust the optical system to be
examined.
22. An exposure apparatus which exposes a predetermined pattern
located at or near an object plane of an optical system to be
examined, over a photosensitive substrate located at or near an
image plane of the optical system to be examined, comprising: the
aberration measuring apparatus according to claim 19.
23. An exposure apparatus comprising the optical system to be
examined, which was adjusted by the adjusting method according to
claim 21, the exposure apparatus configured to expose a
predetermined pattern located at or near an object plane of the
adjusted optical system to be examined, over a photosensitive
substrate located at or near an image plane of the optical system
to be examined.
24. An exposure apparatus, comprising: the catadioptric system
according to claim 1, and the exposure apparatus exposing a
predetermined pattern over a photosensitive substrate by means of
the catadioptric system.
25. A device manufacturing method, comprising: exposing the
predetermined pattern over the photosensitive substrate, using the
exposure apparatus according to claim 22; developing the
photosensitive substrate to which the predetermined pattern is
transferred, thereby to form a mask layer in a shape corresponding
to the predetermined pattern, on a surface of the photosensitive
substrate; and processing the surface of the photosensitive
substrate through the mask layer.
26. A device manufacturing method, comprising: exposing the
predetermined pattern over the photosensitive substrate, using the
exposure apparatus according to claim 24; developing the
photosensitive substrate to which the predetermined pattern is
transferred, thereby to form a mask layer in a shape corresponding
to the predetermined pattern, on a surface of the photosensitive
substrate; and processing the surface of the photosensitive
substrate through the mask layer.
27. An inspection apparatus which inspects a sample, comprising the
catadioptric system according to claim 1, wherein light having
traveled via the sample arranged on the first plane, is guided to
the catadioptric system.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims priority to Provisional Application
No. 61/272,335 filed on Sep. 14, 2009, by the same Applicant, which
is hereby incorporated by reference in its entirety.
BACKGROUND
[0002] 1. Field
[0003] Respective embodiments of the invention relate to a
catadioptric system, aberration measuring apparatus, method of
adjusting an optical system, exposure apparatus, and device
manufacturing method. More particularly, the present invention
relates to a catadioptric system applicable, for example, to an
aberration measuring apparatus mounted on an exposure apparatus for
manufacturing electronic devices by lithography.
[0004] 2. Description of the Related Art
[0005] Photolithography for manufacture of semiconductor devices
and others is carried out using the exposure apparatus which
projects and exposes a pattern image of a mask (or reticle) over a
photosensitive substrate (a wafer, glass plate, or the like coated
with a photoresist) through a projection optical system. In the
exposure apparatus, the demand for resolving power (resolution) of
the projection optical system is becoming higher and higher with
increase in degree of integration of semiconductor devices or the
like. For meeting the demand for resolving power of the projection
optical system, there is the conventionally known liquid immersion
technology to increase the image-side numerical aperture by filling
the interior of the optical path between the projection optical
system and the photosensitive substrate with a medium like a liquid
having a high refractive index.
[0006] For achieving high resolution, the projection optical system
mounted on the liquid immersion type exposure apparatus (which will
also be referred to as "liquid immersion projection optical
system") is required to have extremely small residual aberration.
For example, U.S. Patent Publication No. 2006-0170891 proposes a
configuration in which an aberration measuring apparatus for
measuring wavefront aberration of the liquid immersion projection
optical system is mounted on a substrate stage for holding and
moving the photosensitive substrate.
SUMMARY
[0007] According to an embodiment of the invention, a catadioptric
system of a coaxial type, comprises a first optical system, and a
second optical system. The first optical system forms a point
optically conjugate with an intersecting point with the optical
axis on a first plane intersecting with the optical axis, on a
second plane. The second optical system guides light from the first
optical system to a third plane. In addition, the first optical
system has a first reflecting surface, a second reflecting surface,
and a medium. The first reflecting surface is arranged at or near a
position of the first plane, and has a first light transmissive
portion formed in a central region including the optical axis. The
second reflecting surface has a form of an ellipsoid of revolution
the two focuses of which are aligned along the optical axis in a
state in which one focus is located at or near the first light
transmissive portion, and has a second light transmissive portion
formed in a central region including the optical axis. The medium
fills an optical path between the first reflecting surface and the
second reflecting surface, and has a refractive index of not less
than 1.3. The second optical system has a plurality of lenses.
Light from the intersecting point between the first plane and the
optical axis travels through the first light transmissive portion,
is successively reflected by the second reflecting surface and the
first reflecting surface, and then travels through the second light
transmissive portion to enter the second optical system.
Furthermore, all reflecting surfaces and all refracting surfaces of
the catadioptric system are arranged on an optical axis extending
linearly.
[0008] For purposes of summarizing the invention, certain aspects,
advantages, and novel features of the invention have been described
herein. It is to be understood that not necessarily all such
advantages may be achieved in accordance with any particular
embodiment of the invention. Thus, the invention may be embodied or
carried out in a manner that achieves or optimizes one advantage or
group of advantages as taught herein without necessarily achieving
other advantages as may be taught or suggested herein.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0009] A general architecture that implements the various features
of the invention will now be described with reference to the
drawings. The drawings and the associated descriptions are provided
to illustrate embodiments of the invention and not to limit the
scope of the invention.
[0010] FIG. 1 is an exemplary drawing schematically showing a main
configuration of a catadioptric system according to a typical
mode;
[0011] FIG. 2 is an exemplary drawing schematically showing a
configuration of an exposure apparatus according to an
embodiment;
[0012] FIG. 3 is an exemplary drawing schematically showing a
configuration between a boundary lens and a wafer;
[0013] FIG. 4 is an exemplary drawing schematically showing an
internal configuration of an aberration measuring apparatus
according to an embodiment;
[0014] FIG. 5 is an exemplary drawing schematically showing a
configuration of a catadioptric system according to the first
example;
[0015] FIG. 6 is an exemplary drawing showing transverse aberration
of the catadioptric system according to the first example;
[0016] FIG. 7 is an exemplary drawing schematically showing a
configuration of a catadioptric system according to the second
example;
[0017] FIG. 8 is an exemplary drawing showing transverse aberration
of the catadioptric system according to the second example;
[0018] FIG. 9 is an exemplary drawing schematically showing a
configuration of a catadioptric system according to the third
example;
[0019] FIG. 10 is an exemplary drawing showing transverse
aberration of the catadioptric system according to the third
example;
[0020] FIG. 11 is an exemplary drawing schematically showing a
configuration of a catadioptric system according to the fourth
example;
[0021] FIG. 12 is an exemplary drawing showing transverse
aberration of the catadioptric system according to the fourth
example;
[0022] FIG. 13 is an exemplary flowchart showing manufacturing
blocks of semiconductor devices; and
[0023] FIG. 14 is an exemplary flowchart showing manufacturing
blocks of a liquid crystal device such as a liquid crystal display
device.
DETAILED DESCRIPTION
[0024] Various embodiments according to the invention will be
described hereinafter with reference to the accompanying
drawings.
[0025] The basic configuration and operational effect of a
catadioptric system according to an embodiment will be described
below prior to detailed description of embodiments. The optical
system according to the present embodiment is a catadioptric system
of a coaxial type in which reflecting and refracting surfaces are
arranged on a single optical axis extending linearly. The
catadioptric system is advantageous in terms of aberration
correction and the coaxial type is advantageous in terms of
assembly and optical adjustment of the optical system and, in turn,
in terms of manufacture of the optical system.
[0026] The catadioptric system according to a typical mode of the
present embodiment is provided with a first optical system G1 and a
second optical system G2 arranged in order along the optical axis
AX, as shown in FIG. 1. The first optical system G1 forms a point
optically conjugate with an intersecting point with the optical
axis AX on a first plane P1 intersecting with the optical axis AX,
on a second plane P2. The second optical system G2 guides light
from the first optical system G1 to a third plane P3. For example,
when the catadioptric system is applied to an aberration measuring
apparatus for measuring wavefront aberration of a liquid immersion
projection optical system, the first plane P1 corresponds to an
image plane of the projection optical system and the third plane P3
to a plane in an optical Fourier transform relation with a
wavefront division plane.
[0027] The first optical system G1 has a pair of reflecting
surfaces R11, R12 opposed to each other along the optical axis AX.
The first reflecting surface R11 is arranged at or near the
position of the first plane P1. A first light transmissive portion
(first light pass portion) T11 is formed in a central region of the
first reflecting surface R11 including the optical axis AX. The
second reflecting surface R12 has a form of an ellipsoid of
revolution the two focuses of which are aligned along the optical
axis AX in a state in which one focus is located at or near the
position of the first light transmissive portion T11 of the first
reflecting surface R11. A second light transmissive portion (second
light pass portion) T12 is formed in a central region of the second
reflecting surface R12 including the optical axis AX. The shape of
the second reflecting surface R12 in the first optical system G1
can be an ellipsoid of revolution without higher-order
(second-order and higher) aspherical coefficients. In this case,
the shape of the second reflecting surface R12 can be measured by
spherical surface measuring technology making use of the two
focuses, or can be measured without use of relatively complicated
aspherical surface measuring technology using a null element or the
like, and is thus advantageous in terms of measurement and
formation of the reflecting surface and, in turn, in terms of
manufacture of the optical system.
[0028] As an example, the reflecting surface R11 can be formed on
an optical member (optical block) L11 comprised of an optical
material like silica glass and having a form of a planoconvex lens
shape with a convex surface on the third plane P3 side. Namely, the
reflecting surface R11 is formed by providing a light-blocking
reflecting film M11 in a region except for the first light
transmissive portion T11 on a plane of the optical member L1 on the
first plane P1 side. The reflecting surface R12 is formed by
providing a light-blocking reflecting film M12 in a region except
for the second light transmissive portion T12 on the ellipsoid of
revolution of the optical member L11 on the third plane P3
side.
[0029] The light transmissive portions T11, T12 have, for example,
a circular shape including the optical axis AX and the size
substantially larger than the diffraction limit. As an example, the
second reflecting surface R12 can be formed in the ellipsoidal
shape. The ellipsoid herein is a spheroid the major axis of which
is an axis of revolution, and is also called a prolate or prolate
spheroid. When the second reflecting surface R12 is formed in the
prolate spheroid shape, the axis of revolution of the prolate
spheroid can be made coincident with the optical axis AX.
[0030] The first reflecting surface R11 and the second reflecting
surface R12 are formed on one common optical member L11 (single
optical member without any internal cemented surface corresponding
to an interface between optical members). For this reason, the
optical path between the first reflecting surface R11 and the
second reflecting surface R12 is filled with a medium having the
refractive index of not less than 1.3. The second optical system G2
is, for example, a refracting optical system composed of a
plurality of lenses. FIG. 1 shows only a first lens L21 disposed
nearest to the first optical system G1 and the nth lens L2n
disposed nearest to the third plane P3, out of the plurality of
lenses constituting the second optical system G2. The first lens
L21 is, for example, a positive lens with a convex surface on the
third plane P3 side.
[0031] In the catadioptric system of the present embodiment, the
light from the intersecting point between the first plane P1 and
the optical axis AX passes through the first light transmissive
portion T11, is then successively reflected by the second
reflecting surface R12 and the first reflecting surface R11, and
thereafter travels through the second light transmissive portion
T12 to enter the second optical system G2. Specifically, the light
passing through the first light transmissive portion T11 is
reflected on an effective reflection region except for the second
light transmissive portion T12 in the second reflecting surface R12
and then impinges on the first reflecting surface R11. The light
reflected on an effective reflection region except for the first
light transmissive portion T11 in the first reflecting surface R11
passes through the second light transmissive portion T12 to enter
the second optical system G2.
[0032] In the catadioptric system of the present embodiment, the
second reflecting surface R12 is formed in the ellipsoidal shape
with the two focuses being aligned along the optical axis AX in the
state in which one focus is located at or near the position of the
first light transmissive portion T11. For this reason, without need
for making the aperture of the second reflecting surface R12
excessively large, the beam taken into the first optical system G1
through the first light transmissive portion T11 can be guided to
the second optical system G2, while reducing generation of
spherical aberration. Particularly, the first optical system G1 has
the magnification of an enlargement ratio from the first plane P1
to the second plane P2. By using the first optical system G1 of
this type, it becomes feasible to convert the beam with a large
numerical aperture taken thereinto through the first light
transmissive portion T11, to a beam with a relatively small
numerical aperture and to guide the converted beam to the second
optical system G2.
[0033] When the second light transmissive portion T12 is located at
or near the position of the second plane P2, the light from the
intersecting point between the first plane P1 and the optical axis
AX travels through the first light transmissive portion T11 and
thereafter is focused at or near the position of the second light
transmissive portion T12. Namely, this configuration allows the
sizes of the light transmissive portions T11, T12 to be kept small.
As a result, it is feasible to keep small the center shield portion
of the beam the reflection of which is impeded by the light
transmissive portions T11, T12 on the reflecting surfaces R11, R12.
This means that when the catadioptric system of the present
embodiment is applied to the aberration measuring apparatus, it is
feasible to keep small a central region where the wavefront
aberration cannot be measured on the pupil plane of the projection
optical system (in general, an optical system to be examined). When
the second optical system G2 is configured as a refracting optical
system composed of a plurality of lenses, it is feasible to correct
well for coma, curvature of field, etc. occurring in the first
optical system G1.
[0034] In the catadioptric system of the present embodiment, the
optical path between the first reflecting surface R11 and the
second reflecting surface R12 is filled with the medium (optical
material) having the refractive index of not less than 1.3. For
this reason, it becomes feasible, for example, to take a beam with
the numerical aperture of not less than 1.3 into the first optical
system G1 and, in turn, to apply the catadioptric system to the
aberration measuring apparatus for measuring the wavefront
aberration of the liquid immersion projection optical system. The
medium filling the optical path between the first reflecting
surface R11 and the second reflecting surface R12 can also be a
liquid (in general, a fluid) having the refractive index of not
less than 1.3 at the wavelength of used light, e.g., pure
water.
[0035] In this way, the present embodiment substantializes the
catadioptric system which is applicable, for example, to the
aberration measuring apparatus for measuring the wavefront
aberration of the liquid immersion projection optical system and
which is radially downsized and corrected well for aberration. The
aberration measuring apparatus according to the present embodiment
is provided with the optical system radially downsized and well
corrected for aberration, and is able to measure, for example, the
wavefront aberration of the liquid immersion projection optical
system. An exposure apparatus according to the present embodiment
is able to accurately transfer a pattern onto a photosensitive
substrate, for example, through the liquid immersion projection
optical system with aberration adjusted using aberration
information obtained by the aberration measuring apparatus for
measuring the wavefront aberration.
[0036] In the catadioptric system of the present embodiment, a
positive lens with a convex surface on the third plane P3 side can
be used as the first lens L21 disposed nearest to the first optical
system G1 in the second optical system G2. This configuration
allows the second optical system G2 to be radially downsized and
thus substantializes the totally compact form eventually.
[0037] In the catadioptric system of the present embodiment, the
first reflecting surface R11 and the second reflecting surface R12
are formed on surfaces of one common optical member L11 (single
optical member the shape of which is defined by a plurality of
faces). This ensures the stability of imaging performance of the
optical system. The single optical member, different from an
optical structure constructed by cementing a plurality of optical
members, is an optical member having no internal cemented surface
corresponding to an interface between members. On the other hand,
the third example described later illustrates an application of an
optical structure constructed by cementing an optical member of a
plane-parallel plate shape and an optical member of a planoconvex
lens shape, for example, with an adhesive, an optical contact, or
the like. In this optical structure, the first reflecting surface
R11 is formed on a surface different from a surface cemented to the
optical member of the planoconvex lens shape, in the optical member
of the plane-parallel plate shape. The second reflecting surface
R12 is formed on a surface different from a surface cemented to the
optical member of the plane-parallel plate shape, in the optical
member of the planoconvex lens shape. The optical structure of this
configuration also ensures the stability of imaging performance of
the optical system.
[0038] In the catadioptric system of the present embodiment, the
conic coefficient .kappa. which defines the ellipsoidal surface of
the second reflecting surface R12 can satisfy Condition (1) below.
When the conic coefficient .kappa. satisfies Condition (1) below,
the catadioptric system can be corrected well for spherical
aberration. If the conic coefficient is over the upper limit of
Condition (1), correction will be insufficient for spherical
aberration; if it is below the lower limit, correction will be
excessive for spherical aberration. In either case, the correction
burden of the spherical aberration increases on the second optical
system G2 and the correction itself becomes complicated. When the
catadioptric system of the present embodiment is considered to be
applied, for example, to the aberration measuring apparatus for
measuring the wavefront aberration, a shield portion in a pupil to
be measured, or an unmeasurable region will increase if the range
of Condition (1) is not met.
-0.20<.kappa.<-0.08 (1)
[0039] In the catadioptric system of the present embodiment, the
second optical system G2 can be configured as an imaging optical
system which forms a point optically conjugate with the
intersecting point between the second plane P2 and the optical axis
AX, on the third plane P3. In this configuration, when the
catadioptric system of the present embodiment is applied to the
aberration measuring apparatus, a relay optical system (Fourier
transform optical system) is interposed between the catadioptric
system and a wavefront division surface.
[0040] In the catadioptric system of the present embodiment, a
shield member SM (cf. FIG. 1) is arranged in the optical path
between the first optical system G1 and the third plane P3. This
configuration can prevent the light passing through the second
light transmissive portion T12 without being reflected by the
second reflecting surface R12 from the intersecting point between
the first plane P1 and the optical axis AX, from reaching the third
plane P3. When the second optical system G2 is an imaging optical
system, the shield member SM can be arranged at or near the
position of the pupil of the second optical system G2.
[0041] In the catadioptric system of the present embodiment, the
second plane P2 is positioned in the optical path of gas between
the first optical system G1 and the second optical system G2. In
this configuration, even if there is a defect (bubble, foreign
matter, or the like) inside the optical member L11, it is feasible
to prevent a clear image of the defect from being formed and thus
to reduce influence of the defect on the aberration measurement.
When it is known that there is almost no defect inside the optical
member L11, the first optical system G1 and the second optical
system G2 may be cemented to each other, for example, with an
adhesive, an optical contact, or the like. In this case, the second
plane P2 is positioned in one optical member (corresponding to the
optical member L11 or the lens L21 in FIG. 1) out of a pair of
optical members cemented to each other. This reduces spherical
aberration occurring at the final surface of the first optical
system G1 (corresponding to the surface of the second light
transmissive portion T12 in FIG. 1) and at the first surface of the
second optical system G2 (corresponding to the entrance-side
surface of the lens L21 in FIG. 1) and thus simplifies the
configuration of the second optical system G2.
[0042] The catadioptric system of the present embodiment can be
configured to satisfy Condition (2) below. When Condition (2) is
satisfied, the center shield portions of the beam in the reflecting
surfaces R11, R12 can be kept small. In Condition (2), D is an
axial distance between an extension of the first reflecting surface
R11 and an extension of the second reflecting surface R12, and L an
axial distance between the extension of the first reflecting
surface R11 and the second plane P2.
0.95<L/D<1.05 (2)
[0043] Specifically, when Condition (2) is satisfied, the first
light transmissive portion T11 is limited to the position at or
near the first plane P1 and the second light transmissive portion
T12 is limited to the position at or near the second plane P2. It
allows the center shield portions of the beam in the reflecting
surfaces R11, R12 to be kept small. In other words, when Condition
(2) is not satisfied, the required sizes of the light transmissive
portions T11, T12 become large and it makes the center shield
portions of the beam too large. This means that the center region
unavailable for the measurement of wavefront aberration becomes too
large on the pupil plane of the optical system to be examined, to
apply the optical system to the aberration measuring apparatus.
[0044] A specific embodiment will be described on the basis of the
accompanying drawing. FIG. 2 is an exemplary drawing schematically
showing a configuration of an exposure apparatus according to the
present embodiment. In FIG. 2, X-axis and Y-axis are set in
directions parallel to a transfer surface (exposed surface) of a
wafer W as a photosensitive substrate and Z-axis is set in a
direction perpendicular to the wafer W. More specifically, the XY
plane is set in parallel with a horizontal plane and the +Z-axis is
set upward along the vertical direction.
[0045] Referring to FIG. 2, exposure light (illumination light) EL
is supplied from a light source LS in the exposure apparatus of the
present embodiment. The light source LS applicable herein is, for
example, an ArF excimer laser light source to supply light at the
wavelength of 193 nm. The exposure apparatus of the present
embodiment is equipped with an illumination optical system IL
comprised of an optical integrator (homogenizer), a field stop, a
condenser lens, and so on. The exposure light EL of ultraviolet
pulsed light emitted from the light source LS travels through the
illumination optical system IL to illuminate a reticle (mask)
R.
[0046] A pattern to be transferred is formed on the reticle R and a
pattern region of a rectangular shape with long sides along the
X-direction and short sides along the Y-direction is illuminated.
The light passing through the reticle R travels via a liquid
immersion projection optical system PL to form a reticle pattern at
a projection magnification of a predetermined reduction ratio in an
exposure region (shot area) on the wafer (photosensitive substrate)
W coated with a photoresist. Namely, the pattern image is formed in
the exposure region (or still exposure region) of a rectangular
shape with long sides along the X-direction and short sides along
the Y-direction on the wafer W, optically corresponding to the
illuminated region of the rectangular shape on the reticle R.
[0047] The reticle R is held in parallel with the XY plane on a
reticle stage RST. A mechanism for moving the reticle R in the
X-direction, the Y-direction, and the rotational direction is
incorporated in the reticle stage RST. The reticle stage RST is
configured so that positions in the X-direction, Y-direction, and
rotational direction are measured in real time with reticle laser
interferometers (not shown), and controlled based thereon. The
wafer W is fixed in parallel with the XY plane on a substrate stage
WST through a wafer holder (not shown).
[0048] Specifically, the substrate stage WST has a Z-stage (not
shown) for moving the wafer W in the Z-direction, and an XY stage
(not shown) for moving the Z-stage along the XY plane while holding
the Z-stage. The Z-stage controls the focus position (Z-directional
position) and inclination angle of the wafer W. The Z-stage is
configured so that positions in the X-direction, Y-direction, and
rotational direction are measured in real time with wafer laser
interferometers (not shown), and controlled based thereon. The XY
stage controls the X-direction, Y-direction, and rotational
direction of the wafer W.
[0049] A main control system CR provided in the exposure apparatus
of the present embodiment adjusts the positions of the reticle R in
the X-direction, Y-direction, and rotational direction, based on
measured values by the reticle laser interferometers. Specifically,
the main control system CR transmits a control signal to the
mechanism incorporated in the reticle stage RST, to move the
reticle stage RST, thereby adjusting the position of the reticle R.
Furthermore, the main control system CR adjusts the focus position
(Z-directional position) and inclination angle of the wafer W in
order to match the surface on the wafer W with the image plane of
the projection optical system PL by the autofocus method and
auto-leveling method.
[0050] Specifically, the main control system CR transmits a control
signal to a driving system DR to drive the Z-stage by the driving
system DR, thereby adjusting the focus position and inclination
angle of the wafer W. Furthermore, the main control system CR
adjusts the positions of the wafer W in the X-direction,
Y-direction, and rotational direction, based on measured values by
the wafer laser interferometers. Specifically, the main control
system CR transmits a control signal to the driving system DR to
drive the XY stage by the driving system DR, thereby adjusting the
positions of the wafer W in the X-direction, Y-direction, and
rotational direction.
[0051] During exposure, the pattern image of the reticle R is fully
projected into a predetermined shot area on the wafer W.
Thereafter, the main control system CR transmits a control signal
to the driving system DR to drive the XY stage of the substrate
stage WST along the XY plane by the driving system DR, thereby
implementing block movement of another shot area on the wafer W to
the exposure position. In this manner, the block-and-repeat method
is carried out to repeat the one-shot exposure operation of the
pattern image of the reticle R on the wafer W.
[0052] In another method, the main control system CR transmits a
control signal to the mechanism incorporated in the reticle stage
RST and transmits a control signal to the driving system DR, to
drive the reticle stage RST and the XY stage of the substrate stage
WST at a speed ratio according to the projection magnification of
the projection optical system PL and simultaneously perform
scanning exposure of the pattern image of the reticle R in a
predetermined shot area on the wafer W. Thereafter, the main
control system CR transmits a control signal to the driving system
DR to drive the XY stage of the substrate stage WST along the XY
plane by the driving system DR, thereby implementing block movement
of another shot area on the wafer W to the exposure position.
[0053] In this manner, the block-and-scan method is carried out to
repeat the scanning exposure operation of the pattern image of the
reticle R on the wafer W. Namely, while the positions of the
reticle R and the wafer W are controlled by the driving system DR,
the wafer laser interferometers, etc., the reticle stage RST and
the substrate stage WST and therefore the reticle R and the wafer W
are synchronously moved (scanned) along the short-side direction or
Y-direction of the rectangular still exposure region and
illumination region, whereby scanning exposure of the reticle
pattern is implemented in a region having a width equal to the long
side of the still exposure region and a length according to a
scanning amount (moving amount) of the wafer W, on the wafer W.
[0054] In the present embodiment, as shown in FIG. 3, the optical
path between a boundary lens Lb located nearest to the image plane
in the projection optical system PL, and the wafer W is filled with
a liquid Lm. The boundary lens Lb is a positive lens with a convex
surface on the reticle R side and a plane on the wafer W side. In
the present embodiment, as shown in FIG. 2, the liquid Lm is
circulated in the optical path between the boundary lens Lb and the
wafer W, using a supply and drainage system 21. The liquid Lm used
herein can be pure water (deionized water) which is readily
available in large quantity, for example, in semiconductor
manufacturing factories and others.
[0055] For continuously filling the interior of the optical path
between the boundary lens Lb of the projection optical system PL
and the wafer W with the liquid Lm, applicable techniques include,
for example, the technology disclosed in International Publication
No. WO99/49504, the technology disclosed in Japanese Patent
Application Laid-Open No. 10-303114, and so on. In the technology
disclosed in International Publication No. WO99/49504, the liquid
adjusted at a predetermined temperature is supplied from a liquid
supply device through a supply tube and a discharge nozzle so as to
fill the optical path between the boundary lens Lb and the wafer W
and the liquid is collected from a liquid pool on the wafer W
through a collection tube and an inflow nozzle by the liquid supply
device.
[0056] On the other hand, in the technology disclosed in Japanese
Patent Application Laid-Open No. 10-303114, a wafer holder table is
constructed in a container shape so as to reserve the liquid, and
the wafer W is positioned and held by vacuum contact in a center of
an interior bottom (or in the liquid). The apparatus is configured
so that the tip of the barrel of the projection optical system PL
reaches the interior of the liquid and therefore so that the
wafer-side optical surface of the boundary lens Lb reaches the
interior of the liquid. As the liquid as an immersion liquid is
circulated at a small flow rate in this configuration, it is
feasible to prevent deterioration of the liquid by effects of
antisepsis, mold prevention, and so on. Furthermore, it is also
feasible to prevent aberration variation due to absorption of heat
of the exposure light.
[0057] An aberration measuring apparatus 1 for measuring wavefront
aberration of the liquid immersion projection optical system PL is
mounted on the substrate stage WST. In the aberration measuring
apparatus 1, as shown in FIG. 4, a test reticle TR for aberration
measurement is placed on the reticle stage RST on the occasion of
measuring the wavefront aberration of the projection optical system
PL as an optical system to be examined. In the test reticle TR,
there are a plurality of circular apertures TRa for aberration
measurement two-dimensionally formed (e.g., in a matrix form along
the X-direction and Y-direction).
[0058] The aberration measuring apparatus 1 is equipped with an
objective optical system consisting of a coaxial type catadioptric
system 10 and a Fourier transform optical system 11. Namely, the
first plane P1 of the catadioptric system 10 according to the
present embodiment corresponds to the image plane of the projection
optical system PL, and the third plane P3 corresponds to a plane in
an optical Fourier transform relation with the entrance plane or a
wavefront division plane of a micro fly's eye lens (micro lens
array) 12. In the aberration measuring apparatus 1, light emitted
through one aperture TRa of the test reticle TR and passing through
the projection optical system PL travels via the catadioptric
system 10 and Fourier transform optical system 11 to enter the
micro fly's eye lens 12.
[0059] The micro fly's eye lens 12 is arranged so that its entrance
plane (wavefront division plane) is located at or near the position
of the exit pupil of the objective optical system (10, 11). The
micro fly's eye lens 12 is an optical element constructed, for
example, by arraying a large number of microscopic lenses 12a with
a cross section of a square shape and with a positive refractive
power vertically and horizontally and densely. The micro fly's eye
lens 12 is constructed, for example, by forming the microscopic
lens group in a plane-parallel plate by etching, and functions as a
wavefront dividing element.
[0060] A beam entering the micro fly's eye lens 12 is
two-dimensionally divided by the large number of microscopic lenses
12a and an image of the aperture TRa is formed near the rear focal
plane of each microscopic lens 12a. In other words, a large number
of images of the aperture TRa are formed near the rear focal plane
of the micro fly's eye lens 12. The large number of images of the
aperture TRa formed in this manner are detected by CCD 13 as a
two-dimensional imaging device. The output of CCD 13 is supplied to
a signal processing unit (not shown) in the main control system CR,
for example.
[0061] The aberration measuring apparatus 1 is able to measure (or
determine) the wavefront aberration of the projection optical
system PL about the position of the first light transmissive
portion T11, based on the information about the large number of
images of the aperture TRa supplied from the CCD 13 to the signal
processing unit. Concerning the detailed configuration and action
of the aberration measuring apparatus 1 except for the catadioptric
system 10, reference can be made, for example, to U.S. Patent
Publication No. 2002/0159048 (corresponding to Japanese Patent
Application Laid-Open No. 2002-250677) and U.S. Patent Publication
No. 2008/0043236 (corresponding to International Publication No.
2006/016584). The teachings of U.S. Patent Publication No.
2002/0159048 (corresponding to Japanese Patent Application
Laid-Open No. 2002-250677) and U.S. Patent Publication No.
2008/0043236 (corresponding to International Publication No.
2006/016584) are incorporated herein by reference. The below will
describe the configuration and action of each of examples of the
catadioptric system 10 according to the embodiment.
[0062] In each example, an aspherical surface is represented by
Equation (a) below, where y is a height in a direction normal to
the optical axis, z a distance (sag) along the optical axis from a
tangent plane at a top of the aspherical surface to a position on
the aspherical surface at the height y, r a radius of curvature at
the top, and .kappa. the conic coefficient (conic constant). In
Tables (1), (2), (3), and (4) below, each surface of an aspherical
shape is accompanied by mark * to the right of a surface
number.
z=(y.sup.2/r)/[1+{1-(1+.kappa.)y.sup.2/r.sup.2}.sup.1/2] (a)
First Example
[0063] FIG. 5 is an exemplary drawing schematically showing a
configuration of the first example of the catadioptric system
according to the embodiment. In the catadioptric system 10
according to the first example, the first optical system G1 has the
first reflecting surface R11 and the second reflecting surface R12
and these first reflecting surface R11 and second reflecting
surface R12 are formed on surfaces of the optical member L11
comprised of silica glass (SiO.sub.2) and having a form of a
planoconvex lens shape with a convex surface on the third plane P3
side. Namely, the first reflecting surface R11 is formed on the
plane on the first plane P1 side of the optical member L11 and the
second reflecting surface R12 is formed on the ellipsoidal surface
on the third plane P3 side of the optical member L11. The axis of
revolution of the ellipsoidal surface defining the second
reflecting surface R12 agrees with the optical axis AX.
[0064] The second optical system G2 is composed of, in order from
the entrance side of light, a planoconvex lens L21 with a plane on
the entrance side (first plane P1 side), a positive meniscus lens
L22 with a concave surface on the entrance side, a positive
meniscus lens L23 with a concave surface on the entrance side, a
negative meniscus lens L24 with a convex surface on the entrance
side, a biconvex lens L25, a biconvex lens L26, a negative meniscus
lens L27 with a convex surface on the entrance side, and a negative
meniscus lens L28 with a convex surface on the entrance side. All
the lenses L21 to L28 constituting the second optical system G2 are
made of silica glass.
[0065] The first light transmissive portion T11 is formed in a
circular shape with the radius of 0.02 mm and with the center on
the optical axis AX. The second light transmissive portion T12 is
formed in a circular shape with the radius of 0.113 mm and with the
center on the optical axis AX. The position of the first plane P1,
i.e., the position of the image plane of the projection optical
system PL as an optical system to be examined is coincident with
the position of the first light transmissive portion T11 (or the
position of the first reflecting surface R11). The second plane P2
is located in the gas optical path between the second light
transmissive portion T12 and the entrance-side plane of the
planoconvex lens L21. In the region of the second light
transmissive portion T12, the optical member L11 is formed in the
ellipsoidal shape. In each example, the refractive index of silica
glass for the used wavelength (.lamda.=193.306 nm) is
1.5603261.
[0066] Table (1) below provides values of specifications of the
catadioptric system 10 according to the first example. In Table
(1), NA represents the entrance-side numerical aperture of the
catadioptric system 10, .beta. the magnification of an enlargement
ratio of the first optical system G1, and Om a maximum object
height (the radius of a field region) when the first plane P1 is
assumed to be an object plane. In the first example, since the
position of the first plane P1 is coincident with the position of
the first light transmissive portion T11, the maximum object height
Om is equal to the radius of the first light transmissive portion
T11. Furthermore, the surface number represents an order of each
surface to which the light from the first plane P1 is incident, r a
radius of curvature of each surface (mm), d a space of each surface
(mm), and n the refractive index for the used wavelength
(.lamda.=193.306 nm). The surface space d is assumed to change its
sign at every reflection. The notations in Table (1) also apply to
Tables (2) to (4) below.
TABLE-US-00001 TABLE 1 (MAIN SPECIFICATIONS) NA = 1.4 .beta. = 40
Om = 0.02 mm (SPECIFICATIONS OF OPTICAL MEMBERS) SURFACE NUMBER r d
n .infin. 10.000000 1.5603261 (P1; T11) 1* -13.35000 -10.000000
1.5603261 (R12) 2 .infin. 10.000000 1.5603261 (R11) 3* -13.35000
0.100000 (T12) 4 .infin. 7.864892 1.5603261 (L21) 5 -5.67845
1.088351 6 -7.42428 2.244274 1.5603261 (L22) 7 -7.21893 0.100000 8
-16.12275 2.239416 1.5603261 (L23) 9 -10.00594 0.100000 10
122.40073 1.000000 1.5603261 (L24) 11 13.58740 1.030451 12 23.87230
3.76520 1.5603261 (L25) 13 -18.09664 2.437971 14 22.10529 7.661335
1.5603261 (L26) 15 -16.55372 0.100211 16 32.99440 1.000674
1.5603261 (L27) 17 5.88987 1.284022 18 6.78471 6.532309 1.5603261
(L28) 19 5.84802 105.554500 (P3) (VALUES CORRESPONDING TO
CONDITIONS) L = 10.04810 mm D = 10.0 mm (1) .kappa. = -0.116 (2)
L/D = 1.00481
[0067] FIG. 6 is an exemplary drawing showing the transverse
aberration in the catadioptric system 10 according to the first
example. As apparent from the aberration diagrams of FIG. 6, it is
seen that in the first example the system is corrected well for
aberration though it takes in the beam with the very large
numerical aperture (NA=1.4) at the wavelength of 193.306 nm.
Second Example
[0068] FIG. 7 is an exemplary drawing schematically showing a
configuration of the second example of the catadioptric system
according to the embodiment. In the catadioptric system 10
according to the second example, the first optical system G1 has
the first reflecting surface R11 and the second reflecting surface
R12 and these first reflecting surface R11 and second reflecting
surface R12 are formed on surfaces of the optical member L11
comprised of silica glass and having a form of a planoconvex lens
shape with the convex surface on the third plane P3 side.
Specifically, the first reflecting surface R11 is formed on the
plane on the first plane P1 side of the optical member L11 and the
second reflecting surface R12 is formed on the ellipsoidal surface
on the third plane P3 side of the optical member L11. The axis of
revolution of the ellipsoidal surface defining the second
reflecting surface R12 agrees with the optical axis AX.
[0069] The second optical system G2 is composed of, in order from
the entrance side of light, a planoconvex lens L21 with a plane on
the entrance side (first plane P1 side), a positive meniscus lens
L22 with a concave surface on the entrance side, a positive
meniscus lens L23 with a concave surface on the entrance side, a
negative meniscus lens L24 with a convex surface on the entrance
side, a biconvex lens L25, a biconvex lens L26, a negative meniscus
lens L27 with a convex surface on the entrance side, and a negative
meniscus lens L28 with a convex surface on the entrance side. All
the lenses L21 to L28 constituting the second optical system G2 are
made of silica glass.
[0070] The first light transmissive portion T11 is formed in a
circular shape with the radius of 0.02 mm and with the center on
the optical axis AX. The second light transmissive portion T12 is
formed in a circular shape with the radius of 0.296 mm and with the
center on the optical axis AX. The position of the first plane P1,
i.e., the position of the image plane of the projection optical
system PL as an optical system to be examined is coincident with
the position of the first light transmissive portion T11 (or the
position of the first reflecting surface R11). The second plane P2
is located in the gas optical path between the second light
transmissive portion T12 and the entrance-side plane of the
planoconvex lens L21. In the region of the second light
transmissive portion T12, the optical member L11 is formed in the
ellipsoidal shape. Table (2) below provides values of
specifications of the catadioptric system 10 according to the
second example. In the second example, as in the first example, the
position of the first plane P1 is also coincident with the position
of the first light transmissive portion T11 and thus the maximum
object height Om is equal to the radius of the first light
transmissive portion T11.
TABLE-US-00002 TABLE 2 (MAIN SPECIFICATIONS) NA = 1.35 .beta. = 10
Om = 0.02 mm (SPECIFICATIONS OF OPTICAL MEMBERS) SURFACE NUMBER r d
n .infin. 10.000000 1.5603261 (P1; T11) 1* -13.40000 -10.000000
1.5603261 (R12) 2 .infin. 10.000000 1.5603261 (R11) 3* -13.40000
0.300000 (T12) 4 .infin. 10.129470 1.5603261 (L21) 5 -7.07722
0.100000 6 -13.77373 3.585246 1.5603261 (L22) 7 -10.28167 0.100000
8 -56.53051 2.543081 1.5603261 (L23) 9 -14.74784 0.100000 10
51.21701 1.000000 1.5603261 (L24) 11 11.27565 0.244843 12 11.94743
4.816411 1.5603261 (L25) 13 -28.97152 2.185953 14 16.07307 3.016569
1.5603261 (L26) 15 -96.84564 0.100000 16 12.02571 1.000000
1.5603261 (L27) 17 4.74568 1.269210 18 5.15353 7.233545 1.5603261
(L28) 19 2.60433 14.348958 (P3) (VALUES CORRESPONDING TO
CONDITIONS) L = 10.19067 mm D = 10.0 mm (1) .kappa. = -0.125 (2)
L/D = 1.019067
[0071] FIG. 8 is an exemplary drawing showing the transverse
aberration in the catadioptric system according to the second
example. As apparent from the aberration diagrams of FIG. 8, it is
seen that in the second example the system is corrected well for
aberration though it takes in the beam with the very large
numerical aperture (NA=1.35) at the wavelength of 193.306 nm.
Third Example
[0072] FIG. 9 is an exemplary drawing schematically showing a
configuration of the third example of the catadioptric system
according to the embodiment. In the catadioptric system 10
according to the third example, the first optical system G1 has the
first reflecting surface R11 and the second reflecting surface R12
and these first reflecting surface R11 and second reflecting
surface R12 are formed on surfaces of an optical structure
constructed by cementing a plurality of optical members. The
optical structure is composed of an optical member L12 of a
plane-parallel plate shape comprised of silica glass, and an
optical member L13 comprised of silica glass and having a form of a
planoconvex lens shape with a convex surface on the third plane P3
side, and the plane on the third plane P3 side of the optical
member L12 and the plane on the first plane P1 side of the optical
member L13 are cemented to each other, for example, with an
adhesive, an optical contact, or the like. The first reflecting
surface R11 is formed on the plane on the first plane P1 side of
the optical member L12 and the second reflecting surface R12 is
formed on the ellipsoidal surface on the third plane P3 side of the
optical member L13. The axis of revolution of the ellipsoidal
surface defining the second reflecting surface R12 agrees with the
optical axis AX.
[0073] The second optical system G2 is composed of, in order from
the entrance side of light, a planoconvex lens L21 with a plane on
the entrance side (first plane P1 side), a positive meniscus lens
L22 with a concave surface on the entrance side, a positive
meniscus lens L23 with a concave surface on the entrance side, a
negative meniscus lens L24 with a convex surface on the entrance
side, a biconvex lens L25, and a negative meniscus lens L26 with a
convex surface on the entrance side. All the lenses L21 to L26
constituting the second optical system G2 are made of silica glass.
In the region of the second light transmissive portion T12 the
optical member L13 is formed in a planar shape and the plane
corresponding to the region of the second light transmissive
portion T12 in the optical member L13 and the plane on the first
plane P1 side of the planoconvex lens L21 are cemented to each
other, for example, with an adhesive, an optical contact, or the
like. In other words, the first optical system G1 and the second
optical system G2 are cemented to each other.
[0074] The first light transmissive portion T11 is formed in a
circular shape with the radius of 0.02 mm and with the center on
the optical axis AX. The second light transmissive portion T12 is
formed in a circular shape with the radius of 0.254 mm and with the
center on the optical axis AX. The position of the first plane P1,
i.e., the position of the image plane of the projection optical
system PL as an optical system to be examined is coincident with
the position of the first light transmissive portion T11 (or the
position of the first reflecting surface R11). The second plane P2
is located near the second light transmissive portion T12 in the
optical member L13. Table (3) below provides values of
specifications of the catadioptric system 10 according to the third
example.
[0075] Virtual surfaces in the specifications of the optical
members in Table (3) are cemented surfaces between the optical
member L12 and the optical member L13. The value of D in the values
corresponding to Conditions in Table (3) is an axial distance
between an extension (plane) of the first reflecting surface R11
and an extension (ellipsoidal surface) of the second reflecting
surface R12, but is not an axial distance between the extension of
the first reflecting surface R11 and the second light transmissive
portion T12 of the planar shape. In the third example, as in the
first example and the second example, the position of the first
plane P1 is also coincident with the position of the first light
transmissive portion T11 and thus the maximum object height Om is
equal to the radius of the first light transmissive portion
T11.
TABLE-US-00003 TABLE 3 (MAIN SPECIFICATIONS) NA = 1.3 .beta. = 40
Om = 0.02 mm (SPECIFICATIONS OF OPTICAL MEMBERS) SURFACE NUMBER r d
n .infin. 4.000000 1.5603261 (P1; T11) 1 .infin. 6.000000 1.5603261
(VIRTUAL SURFACE) 2* -13.30000 -6.000000 1.5603261 (R12) 3 .infin.
-4.000000 1.5603261 (VIRTUAL SURFACE) 4 .infin. 4.000000 1.5603261
(R11) 5 .infin. 5.999000 1.5603261 (VIRTUAL SURFACE) 6 .infin.
5.884774 1.5603261 (T12; L21) 7 -3.58495 5.632845 8 -14.84778
7.164699 1.5603261 (L22) 9 -12.43550 0.100000 10 -59.95655 2.010705
1.5603261 (L23) 11 -18.69997 0.100000 12 60.95527 1.000000
1.5603261 (L24) 13 18.10527 1.362545 14 135.04767 2.837707
1.5603261 (L25) 15 -16.64066 9.789441 16 12.08485 6.151255
1.5603261 (L26) 17 7.22350 128.701678 (P3) (VALUES CORRESPONDING TO
CONDITIONS) L = 9.86394 mm D = 10.0 mm (1) .kappa. = -0.105 (2) L/D
= 0.986394
[0076] FIG. 10 is an exemplary drawing showing the transverse
aberration in the catadioptric system according to the third
example. As apparent from the aberration diagrams of FIG. 10, it is
seen that in the third example the system is corrected well for
aberration though it takes in the beam with the very large
numerical aperture (NA=1.3) at the wavelength of 193.306 nm.
Fourth Example
[0077] FIG. 11 is an exemplary drawing schematically showing a
configuration of the fourth example of the catadioptric system
according to the embodiment. In the catadioptric system 10
according to the fourth example, the first optical system G1 has
the first reflecting surface R11 and the second reflecting surface
R12 and these first reflecting surface R11 and second reflecting
surface R12 are formed on surfaces of the optical member L11
comprised of silica glass and having a form of a planoconvex lens
shape with a convex surface on the third plane P3 side.
Specifically, the first reflecting surface R11 is formed on the
plane on the first plane P1 side of the optical member L11 and the
second reflecting surface R12 is formed on the ellipsoidal surface
on the third plane P3 side of the optical member L11. The axis of
revolution of the ellipsoidal surface defining the second
reflecting surface R12 agrees with the optical axis AX.
[0078] The second optical system G2 is composed of, in order from
the entrance side of light, a planoconvex lens L21 with a plane on
the entrance side (first plane P1 side), a positive meniscus lens
L22 with a concave surface on the entrance side, a positive
meniscus lens L23 with a concave surface on the entrance side, a
biconcave lens L24, a biconvex lens L25, a biconvex lens L26, a
negative meniscus lens L27 with a convex surface on the entrance
side, and a positive meniscus lens L28 with a convex surface on the
entrance side. All the lenses L21 to L28 constituting the second
optical system G2 are made of silica glass.
[0079] The first light transmissive portion T11 is formed in a
circular shape with the radius of 0.234 mm and with the center on
the optical axis AX. The second light transmissive portion T12 is
formed in a circular shape with the radius of 0.254 mm and with the
center on the optical axis AX. The position of the first plane P1,
i.e., the position of the image plane of the projection optical
system PL as an optical system to be examined is located 0.1 mm
apart from the position of the first light transmissive portion T11
(or the position of the first reflecting surface R11) toward the
projection optical system PL. The optical path between the first
plane P1 and the first reflecting surface R11 is filled with pure
water. The refractive index of pure water for the used wavelength
(.lamda.=193.306 nm) is 1.435876.
[0080] The second plane P2 is located in the gas optical path
between the second light transmissive portion T12 and the
entrance-side plane of the planoconvex lens L21. In the region of
the second light transmissive portion T12, the optical member L11
is formed in the ellipsoidal shape. Table (4) below provides values
of specifications of the catadioptric system 10 according to the
fourth example. In the fourth example, unlike the first to third
examples, the position of the first plane P1 is not coincident with
the position of the first light transmissive portion T11 and
therefore the maximum object height Om is not equal to the radius
of the first light transmissive portion T11 but is equal to the
radius of a field region on the first plane P1 corresponding to the
first light transmissive portion T11.
TABLE-US-00004 TABLE 4 (MAIN SPECIFICATIONS) NA = 1.3 .beta. = 40
Om = 0.02 mm (SPECIFICATIONS OF OPTICAL MEMBERS) SURFACE NUMBER r d
n .infin. 0.10000 1.435876 (P1) 1 .infin. 10.00000 1.5603261 (T11)
2* -13.45000 -10.00000 1.5603261 (R12) 3 .infin. 10.00000 1.5603261
(R11) 4* -13.45000 0.40000 (T12) 5 .infin. 7.01097 1.5603261 (L21)
6 -6.53351 0.45524 7 -15.76753 2.49739 1.5603261 (L22) 8 -7.15635
1.29617 9 -12.11822 1.73998 1.5603261 (L23) 10 -8.94935 0.39960 11
-25.91075 1.00000 1.5603261 (L24) 12 11.99403 0.49026 13 15.18157
3.91751 1.5603261 (L25) 14 -13.86029 9.90048 15 31.03134 4.94399
1.5603261 (L26) 16 -15.59292 0.10000 17 35.77250 1.00000 1.5603261
(L27) 18 5.86511 0.96192 19 6.78064 1.91330 1.5603261 (L28) 20
9.07296 145.83117 (P3) (VALUES CORRESPONDING TO CONDITIONS) L =
10.05809 mm D = 10.0 mm (1) .kappa. = -0.138142 (2) L/D =
1.005809
[0081] FIG. 12 is an exemplary drawing showing the transverse
aberration in the catadioptric system according to the fourth
example. As apparent from the aberration diagrams of FIG. 12, it is
seen that in the fourth example the system is corrected well for
aberration though it takes in the beam with the very large
numerical aperture (NA=1.3) at the wavelength of 193.306 nm.
[0082] In the aforementioned embodiment, the second optical system
G2 is the imaging optical system for keeping the second plane P2
and the third plane P3 in an optically conjugate relation, and the
catadioptric system 10 and Fourier transform optical system 11
constitute the objective optical system for the aberration
measuring apparatus 1. However, without having to be limited to
this, it is also possible to construct the catadioptric system so
that the second optical system G2 keeps the second plane P2 and the
third plane P3 in an optical Fourier transform relation. In this
case, the position of the third plane P3 is coincident with the
position of the wavefront division plane (the position of the
entrance plane of the micro fly's eye lens 12 in FIG. 4) and
installation of the Fourier transform optical system is omitted. In
the foregoing embodiment, the second light transmissive portion T12
of the first optical system G1 is located near the second plane P2,
but the second transmissive portion T12 may be located at the
position of the second plane P2.
[0083] In the aforementioned embodiment, the catadioptric system 10
is applied to the aberration measuring apparatus 1 for measuring
the aberration of the optical system to be examined (liquid
immersion projection optical system PL). However, without having to
be limited to this, there are a variety of modes of application of
the catadioptric system according to the embodiment. For example,
the catadioptric system of the present embodiment can be applied to
an objective optical system for a spatial image measuring apparatus
for measuring a spatial image of an optical system to be examined.
Specifically, the catadioptric system of the present embodiment can
be used instead of the relay lens system (275, 276, 277, 278) in
the spatial image measuring unit 270 (detecting apparatus)
disclosed in FIG. 23 of U.S. Patent Publication No.
2006-0170891.
[0084] The catadioptric system of the embodiment is able to form an
optical image of a sample by an objective optical system in a state
in which a space between the sample and the tip of the objective
optical system is immersed in a liquid. Therefore, the catadioptric
system can be used as an objective optical system of a detecting
apparatus for detecting a defect, foreign matter, or the like on a
sample by detecting the optical image with an image sensor. The
detecting apparatus of this type can be found with reference, for
example, to the disclosure of U.S. Patent Publication No.
2005/0052642). The teachings of U.S. Patent Publication No.
2005/0052642) are incorporated herein by reference. The
catadioptric system of the embodiment can also be used as an
objective optical system of a microscope for observing an optical
image of the sample. Concerning the liquid immersion microscope of
this type, reference can be made, for example, to the disclosures
of U.S. Pat. No. 7,324,274, U.S. Patent Publication No.
2008/0259446, and U.S. Patent Publication No. 2009/0251691. The
teachings of U.S. Pat. No. 7,324,274, U.S. Patent Publication No.
2008/0259446, and U.S. Patent Publication No. 2009/0251691 are
incorporated herein by reference.
[0085] In the above embodiment, a variable pattern forming device
for forming a predetermined pattern on the basis of predetermined
electronic data can be used instead of the mask (reticle). The
variable pattern forming device applicable herein is, for example,
SLM (Spatial Light Modulator) including a plurality of reflective
elements driven based on the predetermined electronic data. The
exposure apparatus using SLM (Spatial Light Modulator) is
disclosed, for example, in Japanese Patent Application Laid-Open
No. 2004-304135, U.S. Patent Publication No. 2007/0296936
(corresponding to International Publication No. 2006/080285), and
U.S. Pat. No. 7,369,217. Besides the reflective spatial light
modulators of the non-emission type, it is also possible to use a
transmissive spatial light modulator or an image display device of
a self emission type. The catadioptric system of the embodiment can
also be used as an objective lens of the liquid immersion exposure
apparatus disclosed in U.S. Pat. No. 7,369,217. In this case, SLM
for generating the predetermined pattern is disposed on the image
plane of the catadioptric system of the embodiment and the
photosensitive substrate is disposed on the object plane. The
teachings of U.S. Patent Publication No. 2007/0296936
(corresponding to International Publication No. 2006/080285) and
U.S. Pat. No. 7,369,217 are incorporated herein by reference.
[0086] In the above embodiment the shape of the second reflecting
surface R12 of the first optical system G1 may be a shape slightly
modified from the ellipsoid of revolution.
[0087] The exposure apparatus of the foregoing embodiment is
manufactured by assembling various sub-systems containing their
respective components as set forth in the scope of claims in the
present application, so as to maintain predetermined mechanical
accuracy, electrical accuracy, and optical accuracy. For ensuring
these various accuracies, the following adjustments are carried out
before and after the assembling: adjustment for achieving the
optical accuracy for various optical systems; adjustment for
achieving the mechanical accuracy for various mechanical systems;
adjustment for achieving the electrical accuracy for various
electrical systems. The assembling blocks from the various
sub-systems into the exposure apparatus include mechanical
connections, wire connections of electric circuits, pipe
connections of pneumatic circuits, etc. between the various
sub-systems. It is needless to mention that there are assembling
blocks of the individual sub-systems, before the assembling blocks
from the various sub-systems into the exposure apparatus. After
completion of the assembling blocks from the various sub-systems
into the exposure apparatus, overall adjustment is carried out to
ensure various accuracies as the entire exposure apparatus. The
manufacture of the exposure apparatus may be carried out in a clean
room in which the temperature, cleanliness, etc. are
controlled.
[0088] The following will describe a device manufacturing method
using the exposure apparatus according to the above-described
embodiment. FIG. 13 is an exemplary flowchart showing manufacturing
blocks of semiconductor devices. As shown in FIG. 13, the
manufacturing blocks of semiconductor devices include depositing a
metal film on a wafer W to become a substrate of semiconductor
devices (block S40) and applying a photoresist as a photosensitive
material onto the deposited metal film (block S42). The subsequent
blocks include transferring a pattern formed on a mask (reticle) M,
onto each of shot areas on the wafer W, using the exposure
apparatus of the above embodiment (block S44: exposure block), and
developing the wafer W after completion of the transfer, i.e.,
developing the photoresist to which the pattern is transferred
(block S46: development block).
[0089] Thereafter, using the resist pattern made on the surface of
the wafer W in block S46, as a mask, processing such as etching is
carried out on the surface of the wafer W (block S48: processing
block). The resist pattern herein is a photoresist layer in which
depressions and projections are formed in a shape corresponding to
the pattern transferred by the exposure apparatus of the above
embodiment and which the depressions penetrate throughout. Block
S48 is to process the surface of the wafer W through this resist
pattern. The processing carried out in block S48 includes, for
example, at least either etching of the surface of the wafer W or
deposition of a metal film or the like.
[0090] FIG. 14 is an exemplary flowchart showing manufacturing
blocks of a liquid crystal device such as a liquid crystal display
device. As shown in FIG. 14, the manufacturing blocks of the liquid
crystal device include sequentially performing a pattern forming
block (block S50), a color filter forming block (block S52), a cell
assembly block (block S54), and a module assembly block (block
S56). The pattern forming block of block S50 is to form
predetermined patterns such as a circuit pattern and an electrode
pattern on a glass substrate coated with a photoresist, as a plate
P, using the projection exposure apparatus of the above embodiment.
This pattern forming block includes: an exposure block of
transferring a pattern to a photoresist layer, using the projection
exposure apparatus of the above embodiment; a development block of
performing development of the plate P to which the pattern is
transferred, i.e., development of the photoresist layer on the
glass substrate, to form the photoresist layer in the shape
corresponding to the pattern; and a processing block of processing
the surface of the glass substrate through the developed
photoresist layer.
[0091] The color filter forming block of block S52 is to form a
color filter in which a large number of sets of three dots
corresponding to R (Red), G (Green), and B (Blue) are arrayed in a
matrix pattern, or in which a plurality of filter sets of three
stripes of R, G, and B are arrayed in a horizontal scan direction.
The cell assembly block of block S54 is to assemble a liquid
crystal panel (liquid crystal cell), using the glass substrate on
which the predetermined pattern has been formed in block S50, and
the color filter formed in block S52. Specifically, for example, a
liquid crystal is poured into between the glass substrate and the
color filter to form the liquid crystal panel. The module assembly
block of block S56 is to attach various components such as electric
circuits and backlights for display operation of this liquid
crystal panel, to the liquid crystal panel assembled in block
S54.
[0092] The embodiment is not limited just to the application to the
exposure apparatus for manufacture of semiconductor devices, but
can also be widely applied, for example, to the exposure apparatus
for display devices such as the liquid crystal display devices
formed with rectangular glass plates, or plasma displays, and to
the exposure apparatus for manufacture of various devices such as
imaging devices (CCDs and others), micro machines, thin film
magnetic heads, and DNA chips. Furthermore, the embodiment is also
applicable to the exposure block (exposure apparatus) for
manufacture of masks (photomasks, reticles, etc.) on which mask
patterns of various devices are formed, by the photolithography
process.
[0093] The above-described embodiment uses the ArF excimer laser
light (wavelength: 193 nm) as the exposure light, but, without
having to be limited to this, it is also possible to apply the
embodiment to any other appropriate laser light source, e.g., a
light source to supply KrF excimer laser light (wavelength: 248 nm)
or an F.sub.2 laser light source to supply laser light at the
wavelength of 157 nm.
[0094] In the catadioptric system of the embodiment, since the
second reflecting surface is formed in the ellipsoidal shape with
one focus at or near the first light transmissive portion, the beam
with the large numerical aperture taken into the first optical
system can be converted into the beam with the relatively small
numerical aperture and the converted beam can be guided to the
second optical system while suppressing generation of spherical
aberration, without need for making the aperture of the second
reflecting surface excessively large. In the catadioptric system of
the embodiment, the optical path between the first reflecting
surface and the second reflecting surface is filled with the medium
having the refractive index of not less than 1.3. For this reason,
the catadioptric system is able, for example, to take the beam with
the numerical aperture of not less than 1.3 into the first optical
system and, in turn, it can be applied to the aberration measuring
apparatus for measuring the wavefront aberration of the liquid
immersion projection optical system.
[0095] In this manner, the embodiment substantializes the
catadioptric system that is applicable, for example, to the
aberration measuring apparatus for measuring the wavefront
aberration of the liquid immersion projection optical system and
that is radially downsized and corrected well for aberration. The
aberration measuring apparatus according to the embodiment is
provided with the optical system radially downsized and corrected
well for aberration and thus is able to measure, for example, the
wavefront aberration of the liquid immersion projection optical
system. The exposure apparatus according to the embodiment is able
to accurately transfer the pattern to the photosensitive substrate,
for example, through the liquid immersion projection optical system
adjusted in wavefront aberration with the use of the aberration
measuring apparatus for measuring the wavefront aberration as
needed, and therefore to manufacture good devices.
[0096] It is apparent that the present invention can be modified in
many ways in view of the above description of the present
invention. Such modifications should not be construed as a
departure from the spirit and scope of the present invention and
all improvements obvious to those skilled in the art are intended
to be included in the scope of claims which follows.
* * * * *